Abstract:

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The research on ceramic scaffolds for bone tissue engineering is, nowadays, one of the
newest and most attractive topics in the field of materials for biomedical applications.
These scaffolds are aimed to provide supporting or even enhance the reparative capacity of
body. Biphasic calcium phosphates (BCPs) and silicon doped BCP are very interesting
candidates to be used as materials for scaffolds fabrication in bone tissue engineering.
BCPs and silicon doped BCP consist of a mixture of hydroxyapatite (HA) and β-tricalcium
phosphate (β-TCP) or HA and α-tricalcium phosphate (α-TCP), respectively. For the
regenerative purposes BCPs show better performance than HA because of the higher
solubility of β-TCP compound, which facilitate the subsequent bone ingrowth in the
implant. On the other, silicon doped BCP involve silicon that substituted into the apaptite
crystal lattice for phosphorous with the subsequent charge imbalance. HA/α-TCP based
bioceramics exhibits an important improvement of the bioactive behaviour with respect to
non-substituted apatites. This work reviews the procedures to synthesise and fabricate
scaffolds based on HA/β-TCP and silicon stabilised HA/α-TCP. Special attraction has
been paid in the different synthesis methods and to the shaping of final scaffolds. By
knowing the scaffold features at the crystallinity and macrostuctural level, the
biocompatibility and clinical performance can be better understood, which will be also
considered in this review.

Abstract: The development of calcium phosphate ceramics and other related biomaterials for bone graft
involved a better control of the process of biomaterials resorption and bone substitution. The
biphasic calcium phosphate ceramics (BCP) concept is determined by an optimum balance of
the more stable phase of HA and more soluble TCP. The material is soluble and gradually
dissolves in the body, seeding new bone formation as it releases calcium and phosphate ions
into the biological medium
The main attractive feature of BCP ceramic is their ability to form a direct bond with the host
bone resulting in a strong interface. The formation of this dynamic interface is the result of a
sequence of events involving interaction with cells; formation of carbonate hydroxyapatite
CHA (similar to bone mineral) by dissolution/precipitation processes. At the present time,
BCP is commercially available in blocks, particulates, customized design. The need of
material for Minimal Invasive Surgery (MIS) induced the development of a concept of
granules combination with polymer or calcium phosphate cement for injectable/mouldable
bone substitutes. Four types of injectable/mouldable bone substitutes have been developed by
INSERM Nantes University.

Abstract: A new porous structure as a bone tissue engineering scaffold was developed by a freeze-drying method. The porous nanocomposite was prepared from Biphasic Calcium Phosphate (BCP) which was a mixture of 70% hydroxy apatite and 30%ß-TCP (ß-Tricalcium Phosphate). Porogen was naphthalene and gelatin from bovine skin type B was used as polymer. Gelatin was stabilized with EDC (N-(3-dimethyl aminopropyl)-N´-ethyl carbodiimide hydrochloride) by a cross-linking method. The scaffold was characterized by scanning electronic microscope (SEM), Fourier-Transformed Infrared spectroscopy (FTIR). The biocompatibility of this nanocomposite carried out through MTT (3-(4, 5-Dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide, a tetrazole) cell viability assay. Also other properties of scaffold such as morphology, grain size, bending strength were investigated. Highly porous structure with interconnected porosities, good mechanical behavior and high biocompatibility with bone tissue, were benefits of this porous nanocomposite for bone tissue engineering.

Abstract: Calcium phosphate ceramics such as hydroxy apatite (HA), β-tricalcium phosphate (β-TCP) and bicalcium phosphate (BCP) have been used as a bone graft biomaterial because of their good biocompatibility and similarity of chemical composition to natural bones. To increase the mechanical and osteoconductive properties, the granules and spongy type porous bone graft substitutes were prepared by fibrous monolithic process and polyurethane foam replica methods, respectively. The pore sizes obtained using these approaches ranged between 100-600 µm. The cytotoxicity, cellular proliferation, differentiation and ECM deposition on the bone graft substitutes were observed by SEM and confocal microscopy. Moreover, the scaffolds were implanted in the rabbit femur. New bone formation and biodegradation of bone graft were observed through follow-up X-ray, micro-CT analysis and histological findings. After several months (2, 3, 6, 12 and 24 months) of implantation, new bone formation and ingrowths were observed in defect sites of the animal by CaP ceramics and 2 to 3 times higher bone ingrowths were confirmed than that of the normal trabecular bones in terms of total bone volume (BV).

Abstract: Calcium phosphate bone substitutes are widely used for providing support for the in-growth of hard tissue in various medical applications (e.g., dental, orthopedic). Recently, research involving bone substitutes with interconnected open pore structures has focused on improving the mechanical properties of the substitutes and modifying their surfaces with proteins (e.g., collagen, bone morphogenetic protein) to induce early bone formation. In particular, it is highly desirable to develop a functional gradient-structured bone substitute that has the potential to control the bioresoption rate. A porous BCP scaffold was fabricated by the sponge replica method using a PU sponge. The sponge was dip coated three times followed by oven drying, burning out, and microwave sintering. Several approaches were used to fabricate a functional gradient scaffold. TCP was synthesized using the sol-gel process, and it infiltrated into the pore channel that formed after the burning out of the PU sponge. X-ray diffraction analysis characterized the phase identification of the BCP scaffold. Microstructures of the composites were observed using scanning electron microscopy.